Gateguard

---
name: gateguard
description: "Use when fact-forcing gate that blocks Edit/Write/Bash (including MultiEdit) and demands concrete investigation (importers, data schemas, user instruction) before allowing the action. Measurably improves output quality by +2.25 points vs ungated agents. Triggers on \"gateguard\"."
metadata:
  origin: community
---

# GateGuard — Fact-Forcing Pre-Action Gate

A PreToolUse hook that forces Claude to investigate before editing. Instead of self-evaluation ("are you sure?"), it demands concrete facts. The act of investigation creates awareness that self-evaluation never did.

## When to Activate

- Working on any codebase where file edits affect multiple modules
- Projects with data files that have specific schemas or date formats
- Teams where AI-generated code must match existing patterns
- Any workflow where Claude tends to guess instead of investigating

## Core Concept

LLM self-evaluation doesn't work. Ask "did you violate any policies?" and the answer is always "no." This is verified experimentally.

But asking "list every file that imports this module" forces the LLM to run Grep and Read. The investigation itself creates context that changes the output.

**Three-stage gate:**

```
1. DENY  — block the first Edit/Write/Bash attempt
2. FORCE — tell the model exactly which facts to gather
3. ALLOW — permit retry after facts are presented
```

No competitor does all three. Most stop at deny.

## Evidence

Two independent A/B tests, identical agents, same task:

| Task | Gated | Ungated | Gap |
| --- | --- | --- | --- |
| Analytics module | 8.0/10 | 6.5/10 | +1.5 |
| Webhook validator | 10.0/10 | 7.0/10 | +3.0 |
| **Average** | **9.0** | **6.75** | **+2.25** |

Both agents produce code that runs and passes tests. The difference is design depth.

## Gate Types

### Edit / MultiEdit Gate (first edit per file)

MultiEdit is handled identically — each file in the batch is gated individually.

```
Before editing {file_path}, present these facts:

1. List ALL files that import/require this file (search the tree — Glob/Grep, or find/grep via Bash)
2. List the public functions/classes affected by this change
3. If this file reads/writes data files, show field names, structure,
   and date format (use redacted or synthetic values, not raw production data)
4. Quote the user's current instruction verbatim
```

### Write Gate (first new file creation)

```